diff mbox series

[bpf-next,v2,1/5] libbpf: Use __BYTE_ORDER__

Message ID 20211025131214.731972-2-iii@linux.ibm.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series core_reloc fixes for s390 | expand

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netdev/fixes_present success Fixes tag not required for -next series
netdev/patch_count success Link
netdev/tree_selection success Clearly marked for bpf-next
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netdev/cc_maintainers warning 7 maintainers not CCed: john.fastabend@gmail.com yhs@fb.com netdev@vger.kernel.org songliubraving@fb.com kafai@fb.com kpsingh@kernel.org andrii@kernel.org
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netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/verify_fixes success No Fixes tag
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 94 lines checked
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/header_inline success No static functions without inline keyword in header files
bpf/vmtest-bpf-next success VM_Test
bpf/vmtest-bpf-next-PR success PR summary

Commit Message

Ilya Leoshkevich Oct. 25, 2021, 1:12 p.m. UTC 
__BYTE_ORDER is supposed to be defined by a libc, and __BYTE_ORDER__ -
by a compiler. bpf_core_read.h checks __BYTE_ORDER == __LITTLE_ENDIAN,
which is true if neither are defined, leading to incorrect behavior on
big-endian hosts if libc headers are not included, which is often the
case.

Instead of changing just this particular location, replace all
occurrences of __BYTE_ORDER with __BYTE_ORDER__ in libbpf code for
consistency.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tools/lib/bpf/bpf_core_read.h |  2 +-
 tools/lib/bpf/btf.c           |  4 ++--
 tools/lib/bpf/btf_dump.c      |  8 ++++----
 tools/lib/bpf/libbpf.c        |  4 ++--
 tools/lib/bpf/linker.c        | 12 ++++++------
 tools/lib/bpf/relo_core.c     |  2 +-
 6 files changed, 16 insertions(+), 16 deletions(-)

Comments

Daniel Borkmann Oct. 25, 2021, 10:44 p.m. UTC | #1 
On 10/25/21 3:12 PM, Ilya Leoshkevich wrote:
> __BYTE_ORDER is supposed to be defined by a libc, and __BYTE_ORDER__ -
> by a compiler. bpf_core_read.h checks __BYTE_ORDER == __LITTLE_ENDIAN,
> which is true if neither are defined, leading to incorrect behavior on
> big-endian hosts if libc headers are not included, which is often the
> case.
> 
> Instead of changing just this particular location, replace all
> occurrences of __BYTE_ORDER with __BYTE_ORDER__ in libbpf code for
> consistency.

ACK, that is definitely broken as is - we had similar issue back then with the
bpf_{htons,ntohs}() helpers, details: 78a5a93c1eeb ("bpf, tests: fix endianness
selection").

The bpf_core_read.h change I would split out as a separate commit along with a
proper Fixes tag so it could potentially be cherry-picked easier (since the
remainder in here is a cleanup for consistency and not used out of the BPF prog
where this issue exists).

> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>   tools/lib/bpf/bpf_core_read.h |  2 +-
>   tools/lib/bpf/btf.c           |  4 ++--
>   tools/lib/bpf/btf_dump.c      |  8 ++++----
>   tools/lib/bpf/libbpf.c        |  4 ++--
>   tools/lib/bpf/linker.c        | 12 ++++++------
>   tools/lib/bpf/relo_core.c     |  2 +-
>   6 files changed, 16 insertions(+), 16 deletions(-)

Thanks,
Daniel
diff mbox series

Patch

diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h
index 09ebe3db5f2f..e4aa9996a550 100644
--- a/tools/lib/bpf/bpf_core_read.h
+++ b/tools/lib/bpf/bpf_core_read.h
@@ -40,7 +40,7 @@  enum bpf_enum_value_kind {
 #define __CORE_RELO(src, field, info)					      \
 	__builtin_preserve_field_info((src)->field, BPF_FIELD_##info)
 
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 #define __CORE_BITFIELD_PROBE_READ(dst, src, fld)			      \
 	bpf_probe_read_kernel(						      \
 			(void *)dst,				      \
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index ef924fc2c911..0c628c33e23b 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -538,9 +538,9 @@  int btf__set_pointer_size(struct btf *btf, size_t ptr_sz)
 
 static bool is_host_big_endian(void)
 {
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 	return false;
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 	return true;
 #else
 # error "Unrecognized __BYTE_ORDER__"
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 8e05ab44c22a..17db62b5002e 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -1576,11 +1576,11 @@  static int btf_dump_get_bitfield_value(struct btf_dump *d,
 	/* Bitfield value retrieval is done in two steps; first relevant bytes are
 	 * stored in num, then we left/right shift num to eliminate irrelevant bits.
 	 */
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 	for (i = t->size - 1; i >= 0; i--)
 		num = num * 256 + bytes[i];
 	nr_copy_bits = bit_sz + bits_offset;
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 	for (i = 0; i < t->size; i++)
 		num = num * 256 + bytes[i];
 	nr_copy_bits = t->size * 8 - bits_offset;
@@ -1700,10 +1700,10 @@  static int btf_dump_int_data(struct btf_dump *d,
 		/* avoid use of __int128 as some 32-bit platforms do not
 		 * support it.
 		 */
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 		lsi = ints[0];
 		msi = ints[1];
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 		lsi = ints[1];
 		msi = ints[0];
 #else
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 604abe00785f..cd6132c5a416 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1299,10 +1299,10 @@  static int bpf_object__elf_init(struct bpf_object *obj)
 
 static int bpf_object__check_endianness(struct bpf_object *obj)
 {
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 	if (obj->efile.ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
 		return 0;
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 	if (obj->efile.ehdr->e_ident[EI_DATA] == ELFDATA2MSB)
 		return 0;
 #else
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c
index 7bf658fbda80..ce0800e61dc7 100644
--- a/tools/lib/bpf/linker.c
+++ b/tools/lib/bpf/linker.c
@@ -323,12 +323,12 @@  static int init_output_elf(struct bpf_linker *linker, const char *file)
 
 	linker->elf_hdr->e_machine = EM_BPF;
 	linker->elf_hdr->e_type = ET_REL;
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 	linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB;
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 	linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB;
 #else
-#error "Unknown __BYTE_ORDER"
+#error "Unknown __BYTE_ORDER__"
 #endif
 
 	/* STRTAB */
@@ -538,12 +538,12 @@  static int linker_load_obj_file(struct bpf_linker *linker, const char *filename,
 				const struct bpf_linker_file_opts *opts,
 				struct src_obj *obj)
 {
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 	const int host_endianness = ELFDATA2LSB;
-#elif __BYTE_ORDER == __BIG_ENDIAN
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
 	const int host_endianness = ELFDATA2MSB;
 #else
-#error "Unknown __BYTE_ORDER"
+#error "Unknown __BYTE_ORDER__"
 #endif
 	int err = 0;
 	Elf_Scn *scn;
diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c
index 4016ed492d0c..b5b8956a1be8 100644
--- a/tools/lib/bpf/relo_core.c
+++ b/tools/lib/bpf/relo_core.c
@@ -662,7 +662,7 @@  static int bpf_core_calc_field_relo(const char *prog_name,
 			*validate = true; /* signedness is never ambiguous */
 		break;
 	case BPF_FIELD_LSHIFT_U64:
-#if __BYTE_ORDER == __LITTLE_ENDIAN
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
 		*val = 64 - (bit_off + bit_sz - byte_off  * 8);
 #else
 		*val = (8 - byte_sz) * 8 + (bit_off - byte_off * 8);